python字典dict的用法

#字典的添加、删除、修改操作
dict = {“a” : “apple”, “b” : “banana”, “g” : “grape”, “o” : “orange”}
dict[“w”] = “watermelon”
del(dict[“a”])
dict[“g”] = “grapefruit”
print dict.pop(“b”)
print dict
dict.clear()
print dict

#字典的遍历
dict = {“a” : “apple”, “b” : “banana”, “g” : “grape”, “o” : “orange”}
for k in dict:
    print “dict[%s] =” % k,dict[k]

#字典items()的使用
dict = {“a” : “apple”, “b” : “banana”, “c” : “grape”, “d” : “orange”}
#每个元素是一个key和value组成的元组,以列表的方式输出
print dict.items()

#调用items()实现字典的遍历
dict = {“a” : “apple”, “b” : “banana”, “g” : “grape”, “o” : “orange”}
for (k, v) in dict.items():
    print “dict[%s] =” % k, v

#调用iteritems()实现字典的遍历
dict = {“a” : “apple”, “b” : “banana”, “c” : “grape”, “d” : “orange”}
print dict.iteritems()
for k, v in dict.iteritems():
    print “dict[%s] =” % k, v
for (k, v) in zip(dict.iterkeys(), dict.itervalues()):
    print “dict[%s] =” % k, v

#使用列表、字典作为字典的值
dict = {“a” : (“apple”,), “bo” : {“b” : “banana”, “o” : “orange”}, “g” : [“grape”,”grapefruit”]}
print dict[“a”]
print dict[“a”][0]
print dict[“bo”]
print dict[“bo”][“o”]
print dict[“g”]
print dict[“g”][1]

dict = {“a” : “apple”, “b” : “banana”, “c” : “grape”, “d” : “orange”}
#输出key的列表
print dict.keys()
#输出value的列表
print dict.values()
#每个元素是一个key和value组成的元组,以列表的方式输出
print dict.items()

dict = {“a” : “apple”, “b” : “banana”, “c” : “grape”, “d” : “orange”}
it = dict.iteritems()
print it

#字典中元素的获取方法
dict = {“a” : “apple”, “b” : “banana”, “c” : “grape”, “d” : “orange”}
print dict
print dict.get(“c”, “apple”)        
print dict.get(“e”, “apple”)
#get()的等价语句
D = {“key1″ : “value1″, “key2″ : “value2″}
if “key1″ in D:
    print D[“key1″]
else:
    print “None”

#字典的更新
dict = {“a” : “apple”, “b” : “banana”}
print dict
dict2 = {“c” : “grape”, “d” : “orange”}
dict.update(dict2)
print dict
#udpate()的等价语句
D = {“key1″ : “value1″, “key2″ : “value2″}
E = {“key3″ : “value3″, “key4″ : “value4″}
for k in E:
    D[k] = E[k]
print D
#字典E中含有字典D中的key
D = {“key1″ : “value1″, “key2″ : “value2″}
E = {“key2″ : “value3″, “key4″ : “value4″}
for k in E:
    D[k] = E[k]
print D

#设置默认值
dict = {}
dict.setdefault(“a”)
print dict
dict[“a”] = “apple”
dict.setdefault(“a”,”default”)
print dict

#调用sorted()排序
dict = {“a” : “apple”, “b” : “grape”, “c” : “orange”, “d” : “banana”}
print dict 
#按照key排序
print sorted(dict.items(), key=lambda d: d[0])
#按照value排序
print sorted(dict.items(), key=lambda d: d[1])

#字典的浅拷贝
dict = {“a” : “apple”, “b” : “grape”}
dict2 = {“c” : “orange”, “d” : “banana”}
dict2 = dict.copy()
print dict2

#字典的深拷贝
import copy
dict = {“a” : “apple”, “b” : {“g” : “grape”,”o” : “orange”}}
dict2 = copy.deepcopy(dict)
dict3 = copy.copy(dict)
dict2[“b”][“g”] = “orange”
print dict
dict3[“b”][“g”] = “orange”
print dict

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